1. Field of the Invention
This invention relates to a wire harness to be used in electrical wiring for an electrical device or an office automation device such as a copier (PPC), a personal computer (PC), a facsimile device, a video tape recorder, a video camera, and the like, or in electrical wiring in an instrument panel for a motor vehicle.
2. Statement of the Prior Art
It is well known that a wire harness for electrical devices, office automation devices, or the like uses an insulated conductor wiring circuit plate or a flexible plain conductor cable (hereinafter referred to as "FPC") in which a conductor circuit is printed on a base film made of a resin film. A wire harness using the FPC has advantages of facilitating the formation of a circuit in accordance with the arrangement of connectors to be coupled, as well as of closing up and compacting the circuit.
However, since the FPC to be used in the wire harness requires an etching process, when the FPC is formed into multiple layers to make a complicated conductor circuit, it is necessary to carry out a complicated process, such as double etching, on the front and back sides. This results in high cost. Further, since there are few standard common parts among different circuits on account of the construction of the FPC, the FPC is inferior to the application of circuit alternations and the whole of the wire harness must be produced individually. This also results in high costs.
In such a wire harness, the work to connect the FPC to a printed base plate is very troublesome.
For convenience of explanation, the conventional work to connect a conventional FPC to the printed base plate will be described below by referring to FIGS. 17 to 20. FIGS. 17 and 19 are perspective views illustrating the FPC connected to the printed base plate. FIGS. 18 and 20 are cross-sectional views of the respective portions.
The FPC, as shown in FIGS. 17 and 18, is a flexible plate which has a base film 83, strip-like conductors 31 juxtaposed on the film 33, and a coverlet film 32 attached to the conductors 31. Ends or midportions of the conductors 31 are soldered to conductive paths 35 of the printed base plate or the like to be connected.
However, the work for connecting the conductors 31 to a conductive path 35 on the printed base plate 34 is troublesome and takes time, since heat in the soldering copper is transmitted to the coverlet film 32, or excess solder on the connector area causes an electrical short circuit. In order to overcome these shortcomings, Japanese Patent Public Disclosure No. 3-269912 (1991) discloses an FPC, as shown in FIG. 19, which has a connection area 36 exposing the conductors 31 by removing the coverlet film 32 and the base film 33.
Although the FPC disclosed in the above Japanese Patent Public Disclosure No. 3-269912 is easier to connect to the printed base plate 34 in comparison with the conventional FPC having coverlet film 32 on the connection area, the former FPC has the following disadvantages. As shown in FIG. 20, the connection area 36 having no coverlet film 32 or base film 38 is mounted on the printed base plate 34 which is to be connected, a clearance 42 corresponding to the thickness of the base film 33 is defined between both conductors 31 and the conductive path 35. Consequently, soldering the conductors 31 and the conductive path 35 is difficult, consumes a lot of solder and deteriorates the conductivity between the conductors, since the conductors 31 are electrically connected to each other through the solder filled in the clearance.
Further, it is necessary to reinforce the connection area 36 by taping, or to somehow prevent displacement between the conductors during soldering, in order to ensure conductivity on use, since the connection area 36 deteriorates in a mechanical resistance of tension. Accordingly, the above FPC is not suitable for a modern mass production system on account of the connecting work.